1. Field of the Invention
The present invention relates generally to a cellular phone terminal and an intermittent reception control method to be used in the same. More particularly, the invention relates to an intermittent reception control system in a cellular phone terminal.
2. Description of the Related Art
Conventionally, in the cellular phone terminal, communication with a base station is performed by exchanging sub-frames, each consisted of a reception period (paging channel), an idling period and a transmission period. In the reception period, transmission of information necessary in the transmission period to the base station is performed in conjunction with reception of signal from the base station.
On the other hand, when the cellular phone terminal is placed into waiting condition, instead of sequentially receiving the signals from the base station at every reception period, operation to receive signals from the base station at only necessary reception period is repeated. Namely, the operation, in which when reception is performed at certain reception period, reception of the signal from the base station is not performed for a predetermined period, and next reception of the signal from the base station is performed at the next desired reception period, is repeated.
In case of the condition where reception of the signal from the base station is not performed, supply of a high speed clock for operating enabling operation of the cellular phone terminal is stopped and low speed clock is supplied to lower power consumption of the cellular phone terminal. Accordingly, next desired reception period is determined on the basis of result of counting of the low speed clock.
However, since the high speed clock and the low speed clock are supplied independently, these two clocks are not synchronized with each other to cause phase shift therebetween.
In order to solve this problem, in the technology disclosed in Japanese Unexamined Patent Publication No. 2000-36770, a frequency difference and phase difference of the high speed clock and the low speed clock are detected respectively to transit to the next desired reception period at a timing reflecting those frequency difference and the phase difference.
On the other hand, in the technology disclosed in Japanese Unexamined Patent Publication No. 2000-244351, in order to lower power consumption in the cellular phone terminal in waiting state, a temperature compensated crystal oscillator (TCXO) providing high precision clock for accurately receiving the signal is stopped to use only system clock constantly operating to driving a man-machine interface.
In the foregoing conventional cellular phone terminal, it is required to lower power consumption for expanding waiting period, and power consumption has been reduced by the methods set forth above. However, in case of the cellular phone terminal employing a Code Division Multiple Access (CDMA) system or the like, reception process is complicate to require reduction of process amount of a central processing unit (CPU) for enhancing process efficiency to realize saving of power consumption.